Power transmission device for automobile

ABSTRACT

Power transmission device for automobile is disclosed. The power transmission device for automobile comprises a driving shaft( 10 ), an output shaft( 30 ) a transmission( 20 ), a differential gear part( 50 ) and a four-wheel drive part( 60 ). The driving shaft( 10 ) has a plurality of driving gears( 12 ), each of them having a different diameter respectively. The driving shaft( 10 ) is connected to an engine(E). The output shaft( 30 ) is a hollow shaft and outputs power from the driving shaft( 10 ). The transmission( 20 ) has a plurality of speed change gears( 22 ) meshing continuously with the driving gears( 12 ) and also has a brake member braking the speed change gears( 22 ) selectively to transfer power to the output shaft( 30 ). The differential gear part( 50 ) is located at an end portion of the output shaft( 30 ) and controls the amounts of rotation of both right and left front wheels( 42 ). The four-wheel drive part( 60 ) is fixed on the output shaft( 30 ) and transfers power to rear wheels( 44 ) selectively. The power transmission device for automobile controls effectively the amounts of rotation of the wheels and provides a configuration for four-wheel drive device which is simple and compact.

TECHNICAL FIELD

[0001] This invention relates to power transmission device forautomobile, and more particularly, to power transmission which caneffectively drive both front and rear wheels by operation of a gearboxhaving a plurality of planetary gears.

BACKGROUND ART

[0002] An automobile is provided with power transmission device fortransmitting engine power to front or rear wheels.

[0003] Generally, the power transmission device consists of a clutch, agearbox, a differential gear, etc. The clutch couples two working partsin such a way as to permit connection or disconnection at will withoutthe necessity of bringing both parts to rest. The gearbox is thecomplete system of gear wheels for changing the speed from that of aninput shaft to that of an output shaft, or changing the direction ofrotation of a shaft with or without a speed change. The differentialgear is an arrangement of gears that allows one driving wheel of a carto turn faster than the other when the car goes around a corner.

[0004] Various power transmission devices have been designed, and someof them have been disclosed in patent gazette.

[0005] A power transmission device with multiple overdrive is disclosedin U.S. Ser. No. 09/476,616 by the applicant of this application. Agearbox comprises a plurality of speed change gears provided with acarrier having a specific shape. Accordingly as a carrier of one of thespeed change gears is selectively engaged so as to select a desiredspeed and direction of output torque, the power transmission deviceaccomplishes speed change operation effectively. Also, the powertransmission device can be automatically operated, and the configurationthereof is simple and compact.

[0006] However, it is difficult to control wheel speed because theconfiguration between the output shaft on which speed change gears arecoaxially fixed and the wheels is complicated. That is, if normal finalreduction gear and differential gear is used, it is difficult to controlwheel speed, because the configuration of this power transmission deviceis different from that of a conventional power transmission device.

[0007] Additionally, a conventional four-wheel drive for transmittingpower to both front and rear wheels is complicated in the structuralaspect, and cannot accomplish multiple-stage speed change operationeffectively. That is, the four-wheel drive according to the prior art isinstalled at one portion of a speed change device, and a device toselectively connect the speed change device to the four-wheel drive iscomplicated in the structural aspect, thus it is impossible to change anoutput speed in multiple-stage.

DETAILED DESCRIPTION OF THE INVENTION

[0008] In view of the prior art described above, including thedisadvantages and deficiencies of the prior art, it is an object of thepresent invention to provide a four-wheel drive device being capable ofeffectively controlling the speed of left and right wheels, andtransmitting engine power to both front and rear wheels with simpleconfiguration.

[0009] To accomplish the above-mentioned object, the power transmissiondevice according to this invention comprises a driving shaft having aplurality of driving gears and connected to an engine, each of thedriving gears having a different diameter respectively; a hollow outputshaft for outputting power transferred from the driving shaft; atransmission for changing the speed of the output shaft, thetransmission comprising a plurality of speed change gears continuouslymeshing with the driving gears and coaxially aligned with the outputshaft, and a brake member engaging the speed change gears selectively; adifferential gear part for allowing one wheel to turn faster than theother wheel, the differential gear part installed at the end of theoutput shaft; and a four-wheel drive part for transmitting power to bothfront and rear wheels, the four-wheel drive part installed at a portionof the output shaft.

[0010] The differential gear part may comprise a differential gear casecontaining a pair of differential pinions and installed at the end ofthe output shaft; left and right side gears installed in thedifferential gear case and meshing with the differential pinions; a leftaxle having one end connected to the left side gear and the other endconnected to a left wheel via the hollow portion of the output shaft;and a right axle having one end connected to the right side gear and theother end connected to a right wheel.

[0011] The four-wheel drive part may comprise a sun gear having an outerteeth on an outer surface thereof and coaxially aligned with the outputshaft; a plurality of planetary pinions meshing with the outer surfaceof the sun gear and rotatably supported by a carrier; a ring gear havinginner surface on which inner teeth are meshing with the planetarypinions, and outer surface on which outer teeth are shaped like bevelwheel; a controller for controlling transmission of power to the rearwheels by engaging or releasing the carrier; and a driving pinionmeshing at the right angle with the outer teeth of the ring gear, thedriving pinion connected to a propeller shaft for transmitting power tothe rear wheels.

BRIEF DESCRIPTION OF DRAWINGS

[0012]FIG. 1 is a schematic view showing the configuration of apreferred embodiment of the power transmission device according to thepresent invention.

[0013]FIG. 2 is a sectional view showing the differential gear part ofthe power transmission device shown in FIG. 1.

[0014]FIG. 3 is a sectional view showing the four-wheel drive part ofthe power transmission device shown in FIG. 1.

[0015]FIG. 4 is a sectional view showing the configuration of thefour-wheel drive part shown in FIG. 3.

BEST MODE FOR CARRYING OUT THE INVENTION

[0016] Hereinafter, preferred embodiments according to the presentinvention will be described in detail with reference to the drawings.

[0017]FIG. 1 is a schematic view showing the configuration of apreferred embodiment of the power transmission device according to thepresent invention.

[0018] As shown in FIG. 1, the power transmission device according tothe present invention comprises a driving shaft 10 connected to anengine E, a transmission 20, a differential gear part 50, a four-wheeldrive gear 60, and an output shaft 30.

[0019] Driving gears 12 are fixed on the driving shaft 10 and have adifferent diameter respectively. The transmission 20 comprises aplurality of speed change gears 22 and a brake member 70. The speedchange gears 22 are continuously meshing with the driving gears 12. Thebrake member 70 brakes the speed change gears 22 selectively.

[0020] The driving shaft 10, the transmission 20, and the brake member70 will be described schematically because they are disclosed in U.S.patent application Ser. No. 09/476,616 mentioned in the prior art.

[0021] The driving shaft 10 is connected to an output shaft of an engineE. The speed change gears 22 of the transmission 20 are continuouslymeshing with the driving gears 12 of the driving shaft 10. Since adriver operates the brake member 70 by operating a speed change lever ora speed change button, the brake member 70 engages a selected carrier22A of the speed change gear 22. Thus, the power of the driving gear 12is transferred to the output shaft 30 via the speed change gear 22. Onthe contrary, if a driver releases the brake member 70 from the carrier22A, the power of the driving gear 12 isn't transferred to the outputshaft 30.

[0022] The brake member 70 controls power transmission to the outputshaft 30 by braking or releasing the carrier 22A. As described in U.S.Ser. No. 09/476,616 stated in the prior art section of this application,the brake member 70 may comprise a brake shoe for making contact andcausing friction with outer face of the carrier 22A, a push rod forpushing or pulling the brake shoe, a hydraulic drive member for drivingthe push rod, and a select lever for driving the hydraulic drive memberby generating an electric signal.

[0023] In the meanwhile, the output shaft 30 on which each of speedchange gears 22 of the transmission 20 is fixed is hollow. Sun gears(not shown) of the speed change gears 22 are coaxially fixed on theouter surface of the output shaft 30. A left axle 55 is inserted via thehollow portion of the output shaft 30. Also, a differential gear part 50is installed at an end of the output shaft 30.

[0024]FIG. 2 is a sectional view showing the differential gear part ofthe power transmission device shown in FIG. 1.

[0025] As shown in FIG. 2, the differential gear part 50 comprises adifferential gear case 53, a left side gear 54A, a right side gear 54B,a left axle 55, and a right axle 56.

[0026] The differential gear part 50 is installed at an end of theoutput shaft 30. The differential gear part 50 controls the amounts ofrotation of left and right wheels with a rotation proportional to thesum or difference of the amounts of rotation of the other two, whiledriving the front wheels 42 for front wheel drive.

[0027] The differential gear case 53 is fixed at the end of the outputshaft. A pair of differential pinions 52 are symmetrically installed inthe differential gear case 53. The differential pinions 52 rotate orrevolve while being supported by the differential gear case 53.

[0028] The left and right side gears 54A, 54B are installed at bothinternal sides of the differential gear case 53 respectively, and eachof them is meshing with the differential pinion 52.

[0029] An end of the left axle 55 is connected to the left side gear54A, and the other end of the left axle 55 is connected to a left frontwheel 42 via the hollow portion of the output shaft 30. An end of theright axle 56 is connected to the right side gear 54B, and the other endof the right axle 56 is connected to a right front wheel 42.

[0030] The output shaft 30 rotates the differential gear case 53, andthe differential pinions 52 revolve around the center line of thedifferential gear case 53. Thus, the differential gear part 50 transmitspower of the output shaft 30 to the front wheels 42 for front wheeldrive.

[0031] A final reduction gear 80 may be installed between thedifferential gear case 53 and the output shaft 30 in order to reduce theamounts of rotation of the output shaft 30.

[0032] The left axle 55 and right axle 56 may have a uniform velocityjoint.

[0033] The differential gear case 53 and the output shaft 30 may haveteeth formed on the outer surface or a connecting portion thereof.

[0034]FIG. 3 is a sectional view showing the four-wheel drive part ofthe power transmission device shown in FIG. 1. FIG. 4 is a sectionalview showing the configuration of the four-wheel drive part shown inFIG. 3.

[0035] As shown in FIGS. 3 and 4, the four-wheel drive part 60 comprisesa sun gear 62A, a plurality of planetary pinions 62B, a ring gear 62 C,a controller 72, and a driving pinion 66.

[0036] The four-wheel drive part 60 is located at a center portion ofthe output shaft 30. The four-wheel drive part 60 transmits power of theoutput shaft 30 to rear wheels for front wheel drive in order to driveboth front and rear wheels.

[0037] The sun gear 62A is coaxially fixed on the center portion of theoutput shaft 30. The planetary pinions 62B mesh with the outer surfaceof the sun gear 62A and are rotatably supported by a carrier 62D. Thering gear 62C has opposite sides. Inner and outer teeth are formed onthe inner and outer surfaces of the ring gear 62C respectively. Theinner teeth mesh with the planetary pinions 62B. The outer surfaceslopes like bevel wheel.

[0038] The carrier 62D is formed symmetrically on both sides of the ringgear 62C.

[0039] The driving pinion 66 is connected to a propeller shaft 90connected to the final reduction gear 80 of the rear wheels 44. Thedriving pinion 66 meshes with the outer teeth of the ring gear 62C at aright angle.

[0040] The controller 72 controls transmitting power to the rear wheels44 by braking or releasing the carrier 62D. The controller 72 isdisclosed in detail in the U.S. patent application Ser. No. 09/476,616stated as a prior art of this invention. As stated in the U.S. patentapplication Ser. No. 09/476,616, the controller 72 comprises a brakeshoe firmly contacting on the outer surface of the carrier 62D, a pushrod for pushing or pulling the brake shoe, a hydraulic drive member fordriving the push rod, and a select lever for driving the hydraulic drivemember by generating an electric signal.

[0041] At a normal condition, power from an engine E is not transmittedto the rear wheels because the controller 72 does not brake the carrier62D.

[0042] In the meanwhile, if a driver operates the selective lever andshifts to four-wheel drive mode, rotational force of the sun gear 62A istransmitted to the ring gear 62C via each of planetary pinions 62Bbecause the controller 72 brakes the carrier 62D. Thus, the rotationalforce transmitted to the ring gear 62C is transmitted to the rear wheels44 via the driving pinion 66.

[0043] As stated above, the driving pinion 66 is connected to the end ofthe propeller shaft 90 connected to the final reduction gear 80. Thefinal reduction gear 80 transmits power inputted from the driving pinion66 to the rear wheels 44 after applying power at a lower rotationalspeed.

[0044] The four-wheel drive part 60 simultaneously driving both frontand rear wheels has a simple and compact configuration.

[0045] As shown in FIG. 4, the ring gear 62C and the driving pinion 66may be a hypoid gear, a bevel gear, a spiral bevel gear, a worm gear,etc.

[0046] Hereinafter, operations of the preferred embodiment according tothe present invention will be described in detail.

[0047] The four-wheel drive part 60 is installed at the center portionof the output shaft 30, and the ring gear 62C of the four-wheel drivepart 60 meshes with the driving pinion 66. The final reduction gear 80is connected to the rear wheels 44, and is connected to an end of thepropeller shaft 90 of which the other end is connected to the drivingpinion 66. The differential gear part 50 is installed at an end of theoutput shaft 30.

[0048] If the engine E operates, the driving gear 12 rotates. In thiscondition, if a driver operates the speed change button or speed changelever and selects velocity level, the selected brake member 70 brakesthe carrier 22A of the selected speed change gear 22.

[0049] Thus, a planetary gear meshing with a ring gear and a sun gear ofthe speed change gear 22 rotates, and then the power of the drivingshaft 10 is transmitted to the hollow output shaft 30 via the ring gear,the planetary gear, the sun gear.

[0050] The output shaft 30 rotating by the transmitted power rotates thedifferential gear case 53 of the differential gear part 50, and then thedifferential pinion 52 revolves and makes the left and right side gears54A, 54B rotate.

[0051] As the left and right side gears 54A, 54B rotate, the left andright axles 55, 56 rotate because they are connected to the left andright side gears 54A, 54B respectively. Thus, power is transmitted tothe front wheels 42, and the front wheels 42 rotate.

[0052] At this condition, if a front wheel 42, for example, a left frontwheel, is under stress, the differential pinion 52 rotates because theyare connected to the left side gear 54A which is connected to the leftfront wheel 42. Thus, the numbers of rotation of the left and rightfront wheels differ from each other.

[0053] In the meanwhile, if a driver operates the four-wheel drive leveror four-wheel drive button while traveling to drive both the front andrear wheels, the controller 70 brakes the carrier 62D of the four-wheeldrive part 60.

[0054] As the carrier 62D brakes, the rotational force of the sun gear62A fixed on the output shaft 30 is transmitted to the ring gear 62C viathe planetary pinion 62B. Thus, the power transmitted to the ring gear62C rotates the driving gear 12 meshing with the ring gear 62C, and therear wheels 44 rotate.

[0055] The final reduction gear 80 finally reduces the number ofrotations of the propeller shaft 90.

[0056] The four-wheel drive part 60 transmits power to both the frontand rear wheels to correspond to the speed level selected by a driver.That is, the output rotational speed of the four-wheel drive part 60 isinfluenced by the gear ratio of the speed change gear 22 that is meshingwith the driving gear 12 because the four-wheel drive part 60 does notmesh with the driving gear 12 directly but is installed at the outputshaft 30.

[0057] If a driver selects first level, the power corresponding to firstlevel is transferred to the output shaft 30 via the speed change gear22. At this condition, if the driver operates the four-wheel drive part60, the controller 72 brakes the carrier 62D. Thus, the powercorresponding to first level that is transferred to the output shaft 30is transferred to the driving pinion 66 via the sun gear 62A, theplanetary pinion 62B, and the ring gear 62C of the four-wheel drive part60.

[0058] In the meanwhile, if a driver selects 4^(th) or 5^(th) level, asstated above, the power corresponding to 4^(th) or 5^(th) level that istransferred to the output shaft 30 is transferred to the driving pinion66. Also, if a driver selects a backward mode, the power correspondingto the backward mode is transmitted to the driving pinion 66.

[0059] Therefore, the four-wheel drive part 60 can accomplishmulti-stage speed change without separate devices because it isinstalled at the output shaft 30.

[0060] Also, the power transmission device according to the invention asdescribed above can effectively control the numbers of rotation of theleft and right wheels because it has a hollow output shaft of speedchange means that consists of planetary gear sets and a differentialgear part that is installed at an end of the hollow output shaft.

[0061] Also, the configuration of a four-wheel drive part is simple andcompact, and power loss is reduced, because the four-wheel drive part isdirectly installed at the output shaft.

[0062] The invention may be embodied in other specific forms withoutdeparting from the spirit or essential characteristics thereof. Thepresent embodiment is therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. A power transmission device for automobiles comprising: a drivingshaft having a plurality of driving gears and connected to an engine,each of the driving gears having a different diameter respectively; ahollow output shaft for outputting power transferred from the drivingshaft; a transmission for changing the speed of the output shaft, thetransmission comprising a plurality of speed change gears continuouslymeshing with the driving gears and coaxially aligned with the outputshaft, and a brake member engaging the speed change gears selectively; adifferential gear part for allowing one wheel to turn faster than theother wheel, the differential gear part installed at the end of theoutput shaft; and a four-wheel drive part for transmitting power to bothfront and rear wheels, the four-wheel drive part installed at a portionof the output shaft.
 2. The power transmission device for automobilesaccording to claim 1, wherein the differential gear part comprises: adifferential gear case containing a pair of differential pinions andinstalled at the end of the output shaft; left and right side gearsinstalled in the differential gear case and meshing with thedifferential pinions; a left axle having one end connected to the leftside gear and the other end connected to a left wheel via the hollowportion of the output shaft; and a right axle having one end connectedto the right side gear and the other end connected to a right wheel. 3.The power transmission device for automobiles according to claim 1,wherein the four-wheel drive part comprises: a sun gear having an outerteeth on an outer surface thereof and coaxially aligned with the outputshaft; a plurality of planetary pinions meshing with the outer teeth ofthe sun gear and rotatably supported by a carrier; a ring gear having aninner surface on which inner teeth are meshing with the planetarypinions, and an outer surface on which outer teeth are shaped like bevelwheel; a controller for controlling transmission of power to the rearwheels by engaging or releasing the carrier; and a driving pinionmeshing at a right angle with the outer teeth of the ring gear, thedriving pinion connected to a propeller shaft for transmitting power tothe rear wheels.